R replacing values on data frames on the fly

Question

Could someone help me with a wee task I'm stuck with.

I have a df with data (let's call it X) that is as numeric values, which I need to replace with labels. For that I have another df which act as a datamap (let's call it Y), so I actually need to grab a value from X, look it up on Y, to obtain the label that will go into X.

X:
Age Gender Region

 1     2       1

 2     2       3

 2     1       1

Y:

Question Value Label

Age        1      18 to 45
Age        2      Over 45
Gender     1      male
Gender     2      female
Region     1      England
Region     2      Scotland
Region     3      Wales

What I would be looking to obtain is

Z:

Age Gender Region

18 to 45 - female - England

over 45 - female - Wales

over 45 - male - England

Of course my data frames are much bigger, X has like 246 columns and Y has 8k rows and 29 columns. Could you guys give me a hand on how to do such a replacement?

Thanks

deepseefan · Accepted Answer · 2019-10-17 14:36:57Z

0

Using base-r and ifelse

df <- data.frame(Age = c(1,2,2), Gender = c(2,2,1), Region= c(1,3,1))

z$Age = ifelse(df$Age==1, "18 to 45", ifelse(df$Age==2, "Over 45", NA))

z$Gender = ifelse(df$Gender==1, "male", ifelse(df$Gender==2, "female", NA))

z$Region = ifelse(df$Region==1, "England", ifelse(df$Region==2, "Scotland", ifelse(df$Region==3, "Wales",NA)))
z <- data.frame(z)
z

# z
#     Age         Gender   Region
# 1 18 to 45      female   England
# 2  Over 45      female   Wales
# 3  Over 45      male     England

answered Oct 17, 2019 at 14:36

deepseefan

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3 Comments

kaintxu Over a year ago

Thanks a lot, but take into account that's just a tiny fragment of my data sets, so I can't manually do the mapping with ifelse, already thought about that, but I would die doing it like that, plus it would not take into account future data modifications

deepseefan Over a year ago

You might try using a lookup table then.

kaintxu Over a year ago

As i mentioned, the second table is my lookup table, it's about how to reference it the bigger issue

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